There are 108 upanishadh . Among these Upanishadhas the commonlyn well known are Sikshavalli, Aanandavalli, & Bragu valli which form part if Thaithreeya Upanishadh

The Great sage Vedavyaasa has combined Upanishadh, Brahma sootram and Srimadh Bhagavat geetha and termed as sruthi

Thoughts of Upanishadh take as to na narrations on Maharishis contained in bhatarayana

upanishadh pertaning is to proceedings in the court of king of janaka. King of janaka ruled during krutha yuga. the proceedings of this period are narrated two yugas later as Upanishadhas in prasthanathrayam by Bhadatarayana (Veda vyaasa)

There were no writings ahen in the form of palm leaf inscriptions or printing press . All of the narrations were transferred by word of mouth from one to the other and so on . such knowledge is termed as sruthi.

Those days it was customary for a person to clear onesdourts by dipscussing with another person. soch an answer to a question generates in to an Upanishadh . Mostly Upanishadhs are relavant to religinsli wise Sages. However a few relate to everyday life of a common men/woman.

In later years , other scholars have exponunded meanings to these Upanishads basedn on their beliefs.

An adhvaidhi has interpreted to suit the principles of Adhvaidham . so Also a Dwaithi to resonate his ideas of dhvaitham

similarly vishistadhvaithi to propogate his beliefs . for a comon man it is like reading of a doctoral thesis by an elimantrey class student.

Yagyavalgar was a dissiple of Vaisampayana it is customary for one disciple to deliver Mantrakshathai prasadam daily to the king Janaka's palace in the city of Mithila. one day Yagyavalgar had the duty to deliver Mantrakshathai to the palace . however since king Janaka was not presens in his court then , Yagyavalkar simply left the akshatha on top of the seat of king's throne and returned .

By the time king Janaka returned sit on the throne the akshathai had sprouted in to nursert rice plants . surprised at seeing this king janaka sent for yagyavalkar since Yagyavalkar was otherwise busy with his studies ,he dit not appear in the kings court right away so Yagyavalkar was Puniched by Vaisampayanar.

Instead appreciating the special powers vested in Yagyavalkar in getting rice grams to sprout in to plants .he was panished.

As acorollary to this oyr yajur veda lost its pre-eminence as one great veda : but as sukla yajur veda and krishna yajur veda in south it was block krishna yajur veda in north it was white and sukla yajur veda the rituals evolved diferently.

In the pursuit of knowledge during the Maharishi era it was necessary for the diseiple to deote many years in the sertvice of one's guru. for example one has to tend the cow herd diligently and show multiplication of the cow herd to attract attention it is not so now.

Now Vadas, Shastras, epics, and the like are all availablein the form of Books in print many years of toil in shephending the cow herd and multiplying them in the service of a guru is not reqvired what had to be lernt from the gueu is available in the from of Books. Here is an explanation from thaithriya Upanishadh . it is mainly from Sikshavalli, let me refer to Adhilokam, Adi Jyothisham, Adhividhyam, Adhi prajam,Adhilokam AppearanceFirst then herizon followed by the Sky wind jainedforming what we know as the world

Adi Jyothisham Fire AppearanceFirst first subsequently the Sun followed at water resulting in lightning energyas a conjunction.
Adividyam Firdt the Guru Followeed by the disciple resulting in the imparting of knowledge in the form ofupadesam as aconjnction

Adi prajam Mother initially followed by father Resultingin progeny as energy conjuction

Adhyaatmam Lower lip first followed by uppar lip resulting in tongu in the midle forming the conjunction.explanations as abovebring to bear the start of the world aswe know now.

Let as see in how many ways " Bhoor Buvas Suvaha Vyahruthi Manthra is interpretted

(1) Bhoorithiva ayam Lokaha Refers to Bhoo as plant earth (World)
Bhuva ith Yanthriksham Refers to Bhuvaha as hevan
Suvaithyasow lokaha Refers to Suvaha Meaning The planet sun
Maha ith yathithyaha Refers toMahaha the enargy of the sun markingthe world pleasant

(2) Bhoorithiva Agnihi Refers to Bhoo as fire ( Agni)
Bhuva ithi Vayuhu Refers to we as Wind
Suva ithyaathithyaha Refers to Suvaha meaning Sun
Maha ithi Chandraha Refers to world is pleasat due to moon

(3) Bhoorithi vaRuchaha Refers to Bhoo Meaning Rug veda
Bhuvaithi Saamaani Refers to Bhuvaha Meaning Samaveda
Suvaithi Yajugumsi Refers toSuvaha meaning Yajur veda
Mahaithi BrahmaRefers to mahaha meaning Om is the basis for the vedas

(4)Bhurithi Pranaha Refers to meaning Pranan (Life)
Buvaithyapaanaha Refers to meaningnApanan One of ten Vaayu (Excretions)
Suvaithi vyanaha Refers to meaningn Vyaanan One of ten Vaayu (Expansion)
Maha ithyannam Refers to meaningn Maha Meaning Annam (Healthi Food) Food brings Happiness to all beings in the world

Thus " Bur Buvas Suvaha Vyahruthi Manthra has been interpretted By sages in four Different ways

in sikahavalli as part of thaithreeya Upanishdh .Both Ananda valli and brugu vallii Depict creation and set up of Pancha Kosams1(in Vedanta)One term for the five vestures of the body enshrining the soil ( Annamaya, Pranamaya, Manomaya Vignanamaya & Anandamaya Kosas)Step by step Upasana (Practice) towards Mukthi in the form of Examples and anectodes other Upanishadhas like pranavam and uthkadam extol the greatness of Samaveda . likewise all108 Upanishadhas expond different aspects of living . Vedavyasa gave to Rigveda to Bailar Yajurveda to Vaisampayanar Samaveda to Jaimini Atharva veda to Sumanthu this four learned rishis had many disciples who subseqntly imparted In turn different paths of veda eddicts for futurre generations.

now a days we learn by reading books . but it is difficult to follow all these in day to day life due to ever increasing Prsent day demands . However we wonder at the expanse and long range out look of our ancestors for the overall prosperity of future generations.

Om Santhi Santhi Santhihi